JPS62213329A - Radio wave interference detection system - Google Patents

Abstract

PURPOSE:To detect the quantity of radio wave interference with high accuracy by obtaining the error of FM-AM conversion generated in an FM radio equipment from the 1st radio wave interference power ratio obtained from the amplitude component as a power interference error power ratio from the FM demodulated wave and subtracting the error. CONSTITUTION:An output from an FM antenna 10 is converted into an IF signal by the frequency conversion circuit 14 of an FM receiver 12 and its signal is fed to a limiter amplifier 18 and a logarithmic detector 20 via an IF filter 16. Further, an output subjected to amplitude limit by the amplifier 18 is demodulated by an FM demodulator 22 and outputted and fed to an FM-AM converter equivalent circuit 24. The output of the circuit 24 is fed to a power detection circuit 28 via an HPF 26, square detection is applied according to the characteristic of the circuit 24 and the result is fed to a subtraction circuit 30. Further, the output detected by the detector 20 is processed by an HPF 32 and a power detection circuit 34, and the logarithmic detection output is subjected to square detection and the result is fed to the circuit 30. Then the error by the FM-AM conversion is obtained from the demodulated wave as a power interference error power ratio and the radio wave interference quantity is detected with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radio wave interference detection method, and more particularly, to a radio wave interference detection method.
The present invention relates to a radio wave interference detection method that detects the amount of radio wave interference using amplitude components that appear due to radio wave interference in radio equipment that uses waves.

When using a multi-channel mobile communication system such as a car phone system or a mobile phone system, accurate voice information cannot be transmitted if the call quality deteriorates due to radio wave interference. Under such circumstances, it is desirable to avoid radio wave interference by switching channels, but in order to perform such channel switching, it is desirable to accurately measure the amount of radio wave interference in advance.

In the conventional radio interference method, the amplitude component detection voltage is sampled, and the power product between the Hondo wave and the interference wave is calculated from the change in the detected power (square of the detected voltage) over a minute period through arithmetic processing, and at the same time, it is calculated from the detected average power. The power phase of the hondo power and the interference wave is determined, and the ratio between the hondo power and the interference power, that is, the amount of radio wave interference, is determined through arithmetic processing. This is 198
This is a detailed explanation of the high-capacity mobile communication system that was unveiled at the NTT International Symposium held in 2013.

In this radio wave interference detection method, first, the principle of generation of amplitude fluctuation components due to radio wave interference will be explained with reference to FIG.

In FIG. 1, the reference numeral white indicates the FM desired wave vector, the reference numeral 0 indicates the FM interference wave vector, and the reference numeral 0 indicates the FM received wave combined vector.

As is clear from Figure 1, when the frequencies of the desired waves and interference wave 0 are slightly different, the amplitude of the composite wave changes as quickly as the frequency difference between the desired wave and interference wave 0. . That is, the signal is subjected to amplitude modulation, and an amplitude modulation component is generated.

Therefore, by measuring the amount of amplitude fluctuation, it is possible to obtain the radio wave interference ratio (D/U). FIG. 2 is a diagram showing the relationship between the amplitude fluctuation width and the radio wave interference ratio (D/U).

On the other hand, in an FM receiver, the FM
- Due to AM conversion characteristics, an amplitude component is generated by passing the FM modulation signal. In this case, FM-AM conversion becomes particularly noticeable as the passing signal frequency deviates from the center frequency of the intermediate frequency filter.

That is, to explain in detail, in an FM receiver, the passband characteristic of a frequency band limiting filter such as an intermediate frequency filter is not flat, and especially for a filter with a flat delay time characteristic, the passband characteristic is approximately a square-law characteristic. has. Therefore, the FM modulated wave is amplitude-converted by the frequency band limiting filter.

For this reason, in the radio wave interference detection method that measures the amount of amplitude fluctuation to determine the amount of radio wave interference, a problem arises in that it gives a measurement error.

The present invention has been made to overcome the above-mentioned disadvantages, and the present invention is based on the first radio wave interference power ratio obtained from the amplitude component assuming that the amplitude component appears only due to radio wave interference, and the FM-AM obtained from the FM demodulated wave. It is an object of the present invention to provide a radio wave interference detection method capable of obtaining a radio wave interference power ratio in which an error due to FM modulation is reduced by a difference from a radio wave interference error power ratio due to conversion.

Note that the radio wave interference power ratio herein refers to the ratio of interference wave power to desired wave power.

In order to achieve the above object, the present invention provides a radio wave interference detection method that utilizes the appearance of an amplitude component due to radio wave interference in an FM radio, and which detects amplitude fluctuation components due to radio wave interference and amplitude fluctuations occurring within the receiver. A first radio wave interference power ratio determined as the sum of the components is determined, a radio wave interference error power ratio due to FM-AM conversion generated within the FM radio is determined based on the FM demodulated wave, and a radio wave interference error power ratio is determined from the first radio wave interference power ratio. The present invention is characterized in that a value obtained by subtracting the radio wave interference error power ratio is determined and used as the radio wave interference power ratio.

In this way, the radio wave interference error power ratio is subtracted from the first radio wave interference power ratio that includes an error, and the amount of radio wave interference can be detected with high accuracy.

Next, the radio wave interference detection method according to the present invention will be described in detail below with reference to the accompanying drawings, citing preferred embodiments in relation to a device that implements the method.

FIG. 3 is a block circuit diagram for implementing the radio wave interference detection method according to the present invention. In FIG. , especially the tuner part connected to it. Substantially, this FM receiver 12 includes a frequency conversion circuit 14 connected to the output side of the antenna 10, an intermediate frequency filter 16 connected to the output side of the frequency conversion circuit 14, and an intermediate frequency filter 16 connected to the output side of the filter 16. It includes a limiter amplifier 18, a logarithmic detector 20, and an FM demodulator 22 that are connected in parallel.

In this case, an FM-AM conversion equivalent circuit 24 is connected to the output side of the FM demodulator 22, and the output side of this FM-AM conversion equivalent circuit 24 is connected to a bypass filter 26. The output side of the bypass filter 26 is connected to one input terminal of a subtraction circuit 30 via a power detection circuit 28.

Next, the output side of the logarithmic detector 20 is connected to a bypass filter 32.
, and its output side is further connected to the other input terminal of the subtraction circuit 30 via a power detection circuit 34 .

The apparatus for carrying out the radio wave interference detection method according to the present invention is basically constructed as described above, and its operation and effects will be explained next.

First, the output from the antenna 10 is supplied to the frequency conversion circuit 14 and converted into an intermediate frequency signal.

The intermediate frequency signal converted by the frequency conversion circuit 14 is passed through an intermediate frequency filter 16 to a limiter amplifier 18.
and is amplified with limited amplitude. As described above, the amplitude-limited main amplified intermediate frequency signal is supplied to the FM demodulator 22 for FM demodulation. On the other hand, the intermediate frequency signal that has passed through the intermediate frequency filter 16 is supplied to a logarithmic detector 20 and subjected to logarithmic detection.

The logarithmic detection output from the logarithmic detector 20 is supplied to a power detection circuit (square law detection circuit) 34 via a bypass filter 32, and square detection is performed.

Further, the output of the FM demodulator 22 is supplied to an FM-AM conversion equivalent circuit 24 and then to a bypass filter 26.

The output of the bypass filter 26 is supplied to a power detection circuit (square law detection circuit) 28 and subjected to square law detection. Next, the signal is supplied to a subtraction circuit 30 and the output of the power detection circuit 28 is subtracted from the output of the power detection circuit 34.

Next, the operation of one embodiment of the present invention configured as described above will be explained.

The amplitude characteristic of the intermediate frequency filter 16 described above has an FM conversion characteristic of a square characteristic as indicated by reference symbol (al) in FIG. 4, and the amplitude detection characteristic of the logarithmic detector 20 has a In FIG.
The input/output characteristic of the -AM conversion equivalent circuit 24 approximates a square characteristic, and is therefore as shown by reference numeral (d) in FIG.

Therefore, the waveform of the intermediate frequency signal f a (tl) output from the frequency conversion circuit 14 is as shown in FIG. , for example, is shifted by IKHz. In FIG.
m (t) is converted by the FM-AM conversion characteristic of the intermediate frequency filter 16, and the waveform of the converted signal R(t) becomes as shown in (f) in FIG. The signal R(t) is amplitude detected by a logarithmic detector 20,
The waveform of the output signal L (t) of the logarithmic detector 20 is the fourth
In the diagram (illustrated).

Therefore, the output signal L (t) of the logarithmic detector 20 is calculated by the following formula %
Formula % Here, a, a'' are positive proportionality constants, and fo is the center frequency of the passband of the intermediate frequency filter 16.

On the other hand, the intermediate frequency signal f, (t) is the intermediate frequency filter 1
6, the frequency modulated signal hardly changes, and the amplitude is limited by the limiter amplifier 18.
The signal is F MyLiJl by the FM demodulator 22 . This FM demodulated output A F (t) has a waveform indicated by reference symbol (hl) in FIG. 4. The FM demodulated output A F (t) is converted by the FM-AM conversion equivalent circuit 24. The characteristic of the FM-AM conversion equivalent circuit 24 is a square characteristic, and the output 5Q(t) of the FM-AM conversion equivalent circuit 24 is 5Q(t)=b [AF(tl)Q-b
' [f, (t)-fO]'' (2), and its waveform becomes as shown in (1) in FIG. 4. Here, b and b' are proportional constants.

Therefore, suppose a+=b+ and temporarily L(t) and 5Q(t
), the addition result becomes zero, but if a slight phase difference occurs due to circuit conditions, complete erasure cannot be obtained.

Therefore, as in the present example, al == b 1
Then, sufficient cancellation can be obtained by performing power detection (square law detection) on the AC bones of L (t) and 5Q (t) and obtaining the difference.

This will be explained below.

When desired waves and interference waves 0 are supplied to the antenna 10, f) = dsin(ωo t+φd (t)')
・(3) Q=usin((ω.+Δω)t
+φu(t)) ...(4) Here, d and u are proportional constants, and d>u>0ω. is the desired wave angular frequency Δω is the angular frequency difference φd between the desired wave and the interference wave (tl is the phase modulation signal of the desired wave φu (t) is the phase modulation signal of the interference wave, and the vector of the composite wave R has A= 6+0=y(t) sin (ωo(tl+φ(t)
) ・(51Here, ...(6) ...(7) φ, +(1)-φu (tl-φd (t)
-(It is 81.

Here, when looking at d) u, it becomes , and the amplitude fluctuation proportional to u / d due to interference,
A phase modulation disturbance proportional to u/d will occur.

The input FM signal f, (t) that has received interference is as follows.

Here, fl is the frequency of the carrier wave.

The input FM signal f, (t) is converted into 1 a, (f, 1 (t) - f o 'j'' by the FM-AM conversion by the intermediate frequency filter 6)
A normalized amplitude component of −02 is generated. Note that in this case, C7 is a positive proportionality constant. Therefore, the amplitude component R
, 1(t) is R, (tl s d (1+ −CO3(Δωt+φ
,%(t))-a,(f,1(tl-fo)")
・It becomes C1m.

As a result, the logarithmic detection output obtained by detecting the amplitude fluctuation component R,(t) by the logarithmic detector 20, (t) is Ln(t)#k
[-CO3(Δωt+φ, (1) )-a-[(f-
(t)-fo)''-c]] ・C4) is obtained.

Here, c = (fa(t) − f o )”,
Further, k is a positive proportionality constant.

The intermediate frequency signal f, (t) is passed through an intermediate frequency filter 16,
The signal is FM demodulated by the FM demodulator 22 via the limiter amplifier 18, and an FM demodulated wave AF,(t) is obtained.

On the other hand, the logarithmic detection output (t) is the bypass filter 32
The low frequency components due to fading are removed, and the power detection circuit 34 detects the power of interference and ripples due to F'M-AM conversion, and the output Pfi is obtained as follows: P,=L,(t)''.

Furthermore, the FM demodulated wave is added to the FM-AM equivalent circuit 24, and after the DC component is removed by the bypass filter 26,
Power detection is performed by the power detection circuit 28, and the output PC
is Pc = b'((ftt(t)-fo)'-ca1
1-b"((r,,tt+-fo)'-c")・
...αQ is obtained. Here, b'' is a positive proportionality constant.

The output PC of the power detection circuit 28 is subtracted from the output P7 of the power detection circuit 34 by the subtraction circuit 30, and the interference amount detection voltage output is obtained from the following equation. That is, provided that 2 a to b”-
, Z.

As is clear from the formula in a above, the interference amount detection voltage output is a voltage proportional to the square of u/d, so it is easy to calculate the amount of radio wave interference from this, and the amount of interference is F.
Errors due to the M modulation signal have been removed.

Figure 5 shows the relationship between the radio wave interference ratio (D/U) and the interference detection voltage when using the method of the present invention, and the relationship between the change in the amount of FM modulation and the actual measured value of the change when not using the present invention. It shows.

When the method of the present invention is not used, the FM modulation changes from no modulation to the maximum variation m (±2.5 kHz deviation), so in FIG. On the other hand, in the case of the method of the present invention, the change i is about the range A indicated by the downward diagonal line in FIG. 5, and the detection accuracy of the amount of radio wave interference is improved.

As described above, in the present invention, the logarithmic detection output and the FM demodulation output are processed separately, and the amount of radio wave interference is determined by calculating the difference at the power level, so the logarithmic detection output and the FM demodulation output are sampled synchronously or asynchronously. The amount of interference can also be calculated by digital calculation processing using a microprocessor or the like.

As explained above, according to the present invention, in a radio interference detection method that utilizes the fact that an amplified component appears due to radio interference, F
The error due to FM-AM conversion that occurs inside the M radio is
The radio wave interference error power ratio is determined and subtracted from the demodulated wave.

Therefore, errors caused by the FM modulation signal can be removed, and the amount of radio wave interference can be detected with higher accuracy.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to these embodiments, and various improvements and changes in design can be made without departing from the gist of the present invention. Of course.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of the generation of amplitude modulation components due to radio wave interference, Fig. 2 is a diagram showing the relationship between the amplitude fluctuation width and the radio wave interference ratio, and Fig. 3 is a block diagram showing the configuration of an embodiment of the present invention. , FIG. 4 and FIG. 5 are waveform charts and diagrams for explaining the operation of an embodiment of the present invention. 10... Antenna 12... FM receiver 1
4... Frequency conversion circuit 16... Intermediate frequency filter 18... Limiter amplifier 20... Logarithmic detector 22... FM demodulator 24... FM-AM conversion equivalent circuit 26... Bypass filter 28...Power detection circuit 30...Subtraction circuit 32...Bypass filter 34...Power detection circuit Patent applicant Nippon Telegraph and Telephone Corporation Same as above
Japan Radio Co., Ltd. Radio Wave Interference Ratio (D/U) (d B) Procedural Amendment Form Stamped May 23, 1986 2, Title of Invention Radio Wave Interference Detection Method 3, Relationship with Amendment Person Case Patent Applicant Address: 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo
Name Nippon Telegraph and Telephone Corporation ((t
h1 person) Representative: Kou Shin-O 4, Agent: 5, Date of amendment order: Voluntary action (1) In the specification “Detailed Description of the Invention”, page 16, line 10, “..., in Figure 5 , the diagonal line going up to the right is replaced with "...
・In Figure 5, correct the diagonal line downward to the right. (2) Specification “Detailed Description of the Invention”, page 16, No. 12
In the line ``..., in Figure 5, the diagonal line downward to the right...'' is changed to ``
..., in Figure 5, the diagonal line rising to the right...'' is corrected.

Claims (1)

[Claims] (1) A radio wave interference detection method that utilizes the appearance of an amplitude component due to radio wave interference in FM radio equipment, in which the first radio wave is determined as the sum of the amplitude fluctuation component due to radio wave interference and the amplitude fluctuation component generated within the receiver. Find the interference power ratio, F
FM-A generated in the FM radio based on the M demodulated wave
A radio wave interference detection method characterized in that a radio wave interference error power ratio is obtained by M conversion, and a value obtained by subtracting the radio wave interference error power ratio from the first radio wave interference power ratio is determined as the radio wave interference power ratio.